3D Display Design

During my employment at Actuality Systems from 2003-2006, I worked as an optical and software engineer, and managed a NIST funded intiative to design and build next generation 3D displays. Below is a brief description of a few of the designs that I had a large part in developing.

Lenticular 3D displays utilize a cylindircal lens array placed in front of a 2D imaging device such as an LCD screen. Each cylindircal lens covers a set of columns in the displayed image, and each of these columns is converted by the lens from spatial to angular information. The technique is conventient because it produces a very compact optical package. However, it also produces a 3D effect at the cost of reduced spatial resolution. In an attempt to build a 3D display with XGA 1024×768 resolution, we developed a projection engine capable of displaying 25 megapixel images, allowing a XGA lenticular 3D image to be displayed at XGA resolution. The technique works by sequentially scanning 25 XGA images from a high speed DMD projector, producing a composite high resolution image that can is refreshed at video rates. The system consists of a Catadioptric relay system that projects a unit magnification image from a 3-chip DMD engine onto an image scanning module. The scanning module applies a sub-pixel comb filter to the image that is shifted as a function of time. The motion of the filter is synchronized with the images displayed on the DMD, allowing subpixel information to be sequentially filled in, creating a composite high-resolution image.

A system diagram of the spatial-multiplexing 3D display concept.

The projection engine used to implement the super-resolution 2-D backplane from the system diagram above.

A 20 Megapixel image displayed using the projection engine shown on the right.

Scanning Lens Array for View-Sequential 3D

We developed a method to scan the exit pupil of an imaging system for the purpose of projecting view-dependent imagery for the 3D display. The scanning system consists of screen made up of two lenticular or fly’s eye lens arrays placed back-to-back at the image plane of a projection system. The dual lens array screen acts as a field lens according to a principle originally discovered by Denis Gabor (sometime referred to as the Gabor superlens effect). When the optical axis of the two lens arrays are misalgned, the entrance pupil is shifted, and thus the entrance pupil can effectively be scanned by moving one array relative to the other. When lens array movement is applied in synchronization with a high-speed DMD projector, view-dependent 3D imagery can be displayed.

A Gabor superlens scanning system. In the bottom figure, the optical axis of the two lens arrays is aligned, in the top figure, the axis are misaligned, and the exit pupil image is shifted.

The voice coil actuator driven scanning assembly used to shift one of the lens arrays relative to the other at high frequencies.

Scanning Optics for Multi-projector 3D display

We developed a method to sequentially tile projected images from a 2D lens to create the equivalent of 32 projectors from a single high-speed DMD projection system. A DMD projector is fed to a galvonometric scanner that translates the projected image as a function of time, tiling several images sequentially to produce a very high resolution image strip. The image strip is fed to an array of projection lenses that essentially form a synthetic aperture through which an observer can view 3D imagery.

The complete 3D display system. On the left, a projection system is fed to a galvonometer that imposes a translation in the projected image as a function of time.

An image from the projection engine is fed sequentially to each projection lens in the array. A high speed projector is used to that each projection lens is updated fast enough to avoid flicker.